1. Field of the Invention
The present invention relates to an automotive turn indicator and, more particularly, to a turn signal cancellation apparatus for use with a steering wheel and shaft assembly having a steering wheel boss to which the steering shaft is secured.
2. Description of the Prior Art
The prior art turn indicator will be discussed with reference to FIGS. 1 and 2 of the drawings. A steering wheel (not shown) has a boss a through which a steering shaft b extends and is secured thereto by means of a nut c. The shaft b extends through a steering column d to which a turn indicator base e is secured. A bracket f is pivotable with respect to the base e and carries a turn indicator lever g and a cam h which is resiliently supported at one side by a spring i mounted on the base e and has a pair of crests j disposed at the opposite ends of the cam h. The boss a carries a cam actuating pin k mounted on the bottom surface of the boss. The cam h is operable by the lever g so that either of the crests j of the cam is moved into the circular path l of the movement of the cam actuating pin k. Assuming that a car is to be turned to the left, the lever g is first rotated counterclockwise from the neutral position shown by broken lines in FIG. 2 to the solid line position. The rotation of the lever g causes the bracket f to close contacts of a turn indicator switch (not shown) in conventional manner. The upper crests j is now positioned on the path l of movement of the cam actuating pin k. Then, the steering wheel is rotated counterclockwise to turn the car to the left. When the turn of the car is completed, the steering wheel is rotated clockwise to the initial position. This return rotation of the steering wheel moves the cam actuating pin k along the circular path l so that the pin k is contacted with the upper crest j of the cam h to drive the same whereby the bracket f and the lever g are returned to the initial neutral position and the switch contacts are again opened to cancel the turn signal.
In order that the cancellation mechanism may provide a reliable operation, it must be assured that the cam actuating pin k be moved accurately along a predetermined path of movement l. Thus, the cam actuating pin k must be carefully driven into a pin receiving hole m in the bottom surface of the boss so that the pin is not inclined to the axis of the hole m. However, there was a tendency that, because the pin k had to be forcibly driven into the hole m, the pin was inclined to the axis of the hole. After the pin was driven into the hole, therefore, a step was required for correcting the position of the pin with respect to the axis of the hole.
The boss a is fixed to the shaft b by tightening the nut c onto the boss a. The tightening force is applied to a tapered inner peripheral surface n of the axial hole in the boss a. The pin receiving hole m is provided adjacent to the tapered inner peripheral surface n. Should the tightening force of the nut c be unduly large, there occurs a possibility that cracks are produced in the bottom surface of the boss between the hole m and the tapered surface n.